1. Field of the Invention
The present invention relates to a method and an apparatus for generating a preamble, and more particularly, to a method and an apparatus for generating a preamble which is suitable for an ultra-wideband communication system supporting multi-piconet technology using a chaotic sequence.
2. Description of the Related Art
A preamble signal is used in the timing synchronization of signals transmitted between at least two systems. The preamble indicates that a certain system is about to transmit data, and is defined by a string of certain transmission pulses recognized by the communication systems. Reliable timing ensures correct translation of the beginning of information transmission of all the communication systems, and also ensures that all the receiving systems accurately understand when the data transmission begins. Pulses for a preamble vary depending on the network technologies adopted.
FIG. 1 shows the structure of a general preamble. As shown, a preamble generally includes a signal for synchronization, a signal for channel estimation and data for a physical sub-layer. In the communication system, the preamble synchronizes frames and estimates signal degradation in the channel used.
Generally, ‘ultra high frequency communication system’ refers to a system that supports ultra high frequency wireless communications services between a piconet coordinator (PNC) and a device (DEV). For synchronization between the PNC and DEV, a synchronous signal is periodically transmitted to indicate the beginning of the frames. The DEV receives the synchronous signal, synchronizes a frame to the PNC, and estimates signal degradation that may have occurred in the channel to utilize it in the wave detection of the data being received after the frame synchronization. As for the synchronous signal, it is common for a preamble signal agreed upon between the PNC and the DEV to be used.
The DEV receives the preamble signals which are periodically received from the PNC, and determines the frame synchronization in accordance with the strength of the signals being outputted through an internal correlator. The reception performance of the preamble signal depends on the auto-corrrelation property, and a higher auto-correlation property is required.
There are usually a plurality of piconets existing in the ultra-wideband communication system, and interference between neighboring piconets usually causes deterioration in wave detection. Interference with neighboring piconets can also occur in the reception of the preamble signal, which usually degrades the frame synchronization performance. A preamble signal has to be designed with the above-mentioned considered. Further, the preamble signal has to have a good cross-correlation property to support multiple piconets, which means the preamble signal requires a low cross-correlation property.
A similar use of the above-mentioned preamble is found in a UMTS (Universal Mobile Telecommunication System) of wideband CDMA. The UMTS has a plurality of slots in the frame, and a synchronous signal indicating the beginning of the slots. The frame synchronous signal is periodically transmitted between a base station and a terminal according to a predetermined sequence. However, because the UMTS is designed to operate optimally in a cellular communication environment, it is somewhat impractical to employ it in an ultra-wideband communication system. Accordingly, a preamble, which is optimum for use in ultra-wideband communication, is required.